Note: Descriptions are shown in the official language in which they were submitted.
CA 02968923 2017-05-25
WO 2016/087876 PCT/GB2015/053725
Printing Apparatus
This invention relates to apparatus for printing onto cylindrical structures
and to associated methods of printing onto cylindrical structures.
In the field of industrial can manufacture, it is typical that the finished
product requires some form of decoration in the form of printed indicia.
Specialist
printing machines are known to provide continuous, mass printing onto cans at
a
high throughput. These printing machines are commonly known as "decorators"
in the art. At the present time, there are two main decorator designs which
are in
common commercial use, although there are additional, smaller volume
manufacturers as well. The two main designs are commonly known as the
"Concord" and "Rutherford" machines. Although the precise constructional
details of the Concord and Rutherford machines differ, in essence they use the
same approach to printing onto cans. This approach is a variant of offset
printing. More specifically, the decorators comprise a plurality of inkers.
Each
inker is associated with a different colour, and has a printing plate for that
colour.
Each inker is configured to distribute ink of the correct colour onto the
printing
plate. The printing plate has a raised portion corresponding to the desired
image
for the particular colour in question. It will be apparent that, for example,
a six
inker decorator machine can print six colours, and an eight inker decorating
machine can print eight colours. The ink from the print plate of each inker is
transferred onto the surface of one of a number of blankets. The intention is
that
the blanket and the print cylinders of all of the inkers are mutually
positioned and
oriented such that the different coloured inks are in proper registration.
When
proper registration is achieved, the pattern of multiply coloured inks on the
blanket corresponds to the desired indicia. The decorator machines comprise a
plurality of blankets which are disposed on a rotating blanket wheel. As the
wheel rotates, a blanket which has had all of the inks transferred to it in
the
desired pattern is brought into contact with a suitable conveyor system which
typically uses a number of mandrels on a mandrel wheel. The decorator
2
machine is configured so that each can is brought into contact with a blanket
so that
the full multicoloured indicia is transferred to the surface of the can.
It is inevitable that during a continuous can printing process, some
misregistration of one or more of the colours will occur. Traditionally,
misregistration
problems have been corrected manually. More specifically, any misregistration
is
detected by manual inspection of the printed cans. If a misregistration is
identified,
then it has been necessary to shut down printing for a period of time whilst
manual
adjustments of the inkers are made. This is an inefficient process for at
least two
reasons. Firstly, there is a time lag before a misregistration is identified
which can
result in can spoilage. Secondly, it is inefficient and undesirable to shut
down a
continuous process for any period of time.
The present invention, in at least some of its embodiments, addresses the
above
described problems. Additionally, the present invention provides improved
arrangements for controlling the position of the print cylinders.
According to a first aspect of the invention there is provided apparatus for
printing onto cylindrical structures comprising:
a plurality of inker devices each comprising a print cylinder and one or more
servomotors for adjustably controlling the position or orientation of the
print cylinder;
a blanket device comprising a plurality of print blankets, wherein the blanket
device is configured to bring each print blanket into contact with the print
cylinders to
transfer ink from the print cylinders to a print blanket of the blanket
device, and to
bring each print blanket into contact with a cylindrical structure to achieve
printing
thereon;
a transporter for transporting cylindrical structures into and out of contact
with
the print blanket; and
CA 2968923 2018-09-14
3
an automatic print correction system comprising a print inspection device for
detecting a misregistration of ink transferred from one or more of the print
cylinders
onto a print blanket, and a controller for controlling the servomotors of the
print
cylinders to correct the misregistration in response to data received from the
print
inspection device.
In this way, the above described problems can be solved. In particular,
detection of misregistrations can take place quickly. Also, misregistrations
can be
corrected without stopping the printing process.
The print detection device may inspect the print blankets to detect a
misregistration.
Alternatively, the print detection device may inspect the printed cylindrical
structures to detect a misregistration. Alternatively still, the print
detection device may
inspect the print cylinders to detect a misregistration.
The print detection device may comprise a camera. The print detection device
may comprise a single camera, or a plurality of cameras.
The print cylinders may each have a longitudinal adjustment servomotor. The
longitudinal adjustment servomotor may adjustably control the longitudinal
position of
its respective print cylinder. The longitudinal adjustment servomotors may be
controlled by the controller. The print cylinders may be each connected to
their
respective longitudinal adjustment servomotor through a print shaft. At least
a portion
of the print shaft may be movable by the longitudinal adjustment servomotor so
as to
adjustably control the longitudinal position of its respective print cylinder.
The print
shafts may each comprise an outer shaft member and an inner shaft member. The
inner shaft member may be reciprocable within the
CA 2968923 2018-09-14
CA 02968923 2017-05-25
WO 2016/087876 PCT/GB2015/053725
4
outer shaft member. The inner shaft member may be connected to its respective
longitudinal adjustment servomotor and print cylinder so that the longitudinal
adjustment servomotor can adjust the longitudinal position of the print
cylinder
by moving the inner shaft member. In practice, commercial decorator apparatus
are configured so that the longitudinal direction is in the vertical, and a
longitudinal adjustment alters the vertical position of a print cylinder.
The print cylinders may each have an angular adjustment servomotor.
The angular adjustment servomotors may adjustably control the angular
orientation of their respective print cylinders about a rotational axis. The
angular
adjustment servomotors may be controlled by the controller.
The apparatus may further comprise a drive mechanism. The print
cylinders may each be connected to a print shaft which carries a gear, the
gear
being driven by the drive mechanism to cause the print cylinder to rotate
about
the rotational axis. The angular adjustment servomotor may be arranged to
alter
the operation of the gear so as to adjustably control the angular orientation
of its
respective print cylinder. The gear may be a backslash gear. The backslash
gear carries gear teeth which may be inclined at an angle with respect to the
longitudinal axis of the print shaft. The angular adjustment servomotor may
adjust the longitudinal position of the backslash gear which in turn results a
rotational adjustment of the print cylinder about its rotational axis. In this
way,
the angular orientation of the print cylinder can be controlled.
The gear may be slideable along the print shaft under the control of
angular adjustment servomotor. Each angular adjustment servomotor may be
connected to one or more cam followers which follow a cam. The cam may be
disposed on the print shaft and form part of or be connected to a hub. A hub
may be slideable along the print shaft. The gear may be mounted on the hub. In
practice, the rotational axis corresponds to the longitudinal axis of the
print
cylinder. Commercial decorator apparatus are configured so that the rotational
axis is a vertical axis.
CA 02968923 2017-05-25
WO 2016/087876 PCT/GB2015/053725
The apparatus may print onto cans. The transporter may be configured to
transport cans into and out of contact with the print blankets. The
transporter
may comprise a plurality of mandrels for holding the cans. The cans may be
metallic cans, such as aluminium, or maybe formed from another material. The
cans may be beverage cans.
Typically, the controller comprises a computer or another device or
system which utilises a microprocessor. The controller may comprise a
graphical
interface.
The print cylinder may comprise a main portion and a print plate which
may be removeably attached to the main portion. The print plate may be
removeably attached to the main portion by magnetic attachment. The print
plate
may comprise raised features corresponding to a desired print pattern.
lndicia of any desired kind may be printed onto the cans. The indicia may
comprise one or more of an image, a design, a logo, or words.
The print cylinder may each print one or more registration indicia onto the
print blankets. The print blankets may each comprise one or more corresponding
registration features. Misregistration of ink transferred onto a print blanket
may
be detected by detecting a misregistration between a registration indicia
printed
by a print cylinder and the corresponding registration feature on a print
blanket.
The misregistration may be corrected so that a printed registration indicia
and its
corresponding registration feature overlap, and preferably fully overlap. The
registration indicia and registration features may be any convenient shape or
symbol. For example, dots, lines or crosses may be used. The registration
features may be located towards the edge of the print blankets. The print
detection device may be configured to only detect registration indicia and
registration features, or at least to monitor only a subset of entire printing
field.
This can reduce the complexity of the print inspection system.
6
According to a second aspect of the invention there is provided a method of
printing onto cylindrical structures comprising the steps of:
operating a plurality of inker devices to apply ink to a plurality of print
cylinders, each inker device having one or more servomotors for adjustably
controlling the position or orientation of its print cylinder;
operating a blanket device comprising a plurality of print blankets, and
transferring ink from the print cylinders to a print blanket of the blanket
device and
transferring ink from the print blanket to a cylindrical structure to achieve
printing
thereon; and
automatically detecting a misregistration of ink transferred from one or more
of
the print cylinders onto the print blanket and automatically controlling the
servomotors
of the print cylinders to correct the misregistration in response to the
detection of a
misregistration.
It is advantageous that both the automatic detection of a misregistration and
the automatic control of the servomotors to correct the misregistration can be
performed as part of a continuous printing process. In other words, the
process
does not have to be stopped in order for the misregistration to be corrected.
According to a third aspect of the invention there is provided apparatus for
printing onto cylindrical structures comprising:
a plurality of inker devices each comprising a print cylinder, a print shaft
connected to the print cylinder, and a servomotor for adjustably controlling
the
position of the print cylinder;
a blanket device comprising a plurality of print blankets, wherein the blanket
device is configured to bring each print blanket into contact with the print
cylinders
CA 2968923 2018-09-14
7
to transfer ink from the print cylinders to the print blanket, and to bring
each print
blanket into contact with a cylindrical structure to achieve printing thereon;
and
a transporter for transporting a cylindrical structure into and out of contact
with
the print blanket;
wherein, in each inker device, the print shaft comprises an outer shaft member
and an inner shaft member which is reciprocable within the outer shaft member,
and
the inner shaft member is connected to the servomotor.
In this way, an extremely convenient and accurate means is provided for
adjusting and controlling the position of the print cylinder. The arrangement
is space
saving, and permits easy maintenance. Additionally, it is convenient to
provide a
retrofit to an existing decorator apparatus. The third aspect of the invention
can be
conveniently incorporated into decorators of the Rutherford type. However, the
invention is not limited in this regard, and this aspect of the invention can
be
incorporated into other decorator designs.
Whilst the invention has been described above, it extends to any inventive
combination of the features set out above, or in the following description,
drawings
or claims. For example, any feature described in relation to one aspect of the
invention is considered to be disclosed also in relation to another aspect of
the
invention.
Embodiments of apparatus and methods in accordance with the invention will
now described with reference to the accompanying drawings, in which:
Figure 1 is a plan view of a decorator apparatus of the invention;
CA 2968923 2018-09-14
CA 02968923 2017-05-25
WO 2016/087876 PCT/GB2015/053725
8
Figure 2 shows (a) a side view and (b) a cross sectional side view of a
print cylinder and print shaft of the invention; and
Figure 3 shows a graphical interface for use by a user.
Figure 1 shows a decorator apparatus of the invention, depicted generally
at 10. The decorator apparatus 10 comprises a plurality of inkers 12a, 12b,
12c,
12d, 12e, 12f and plurality of blankets 14a, 14b, 14c, 14d, 14e, 14f, 14g,
14h.
The blankets are disposed on a blanket wheel 16. The blanket wheel 16 rotates
so as to bring the blankets into contact with the inkers to transfer ink onto
the
blankets. The rotation of the blanket wheel 16 also brings each blanket into
contact with a can 18 so as to transfer the ink onto the surface of the can.
The
cans 18 are transported into and out of contact with the blankets by a
conveyor
system 20. In the embodiment shown in Figure 1, there are six inkers 12 which
enables up to six different colour inks to be used to form the complete
indicia
which is printed onto the cans 18. Also in the embodiment shown in Figure 1,
the
decorator apparatus 10 comprises eight blankets 14. It will be appreciated
that
the invention is not limited in this regard, and in principle any suitable
numbers
of inkers and blankets might be utilised.
The design and operation of the blankets, blanket wheel and conveyor
can be essentially conventional in nature. Therefore, it is not necessary to
provide a further, more detailed discussion of these portions of the decorator
apparatus 10. The inkers comprise a print cylinder which is rotated by a print
shaft. These aspects of the inkers and described in more detail below. Other
features of the inkers, such as the arrangement for applying ink to the print
cylinders, are essentially conventional in nature. Therefore, a more detailed
discussion of those portions of the inkers is not necessary. The decorator
apparatus 10 further comprises a camera 22 and a controller device 24.
Figure 2 shows the printer cylinder 200 and print shaft 202 of the inkers
12. The print cylinder 200 has a print plate 204 disposed thereon. The print
CA 02968923 2017-05-25
WO 2016/087876 PCT/GB2015/053725
9
cylinder 200 is magnetic and the print plate 204 is formed from a metal so
that
the print plate 204 is retained in place. The print plate 204 has raised
features
which correspond to the print pattern for the ink colour which is applied by
the
particular inker which the print cylinder 200 is associated with. The print
shaft
202 comprises an outer print shaft 202a and an inner print shaft 202b. The
outer
print shaft 202b has a print cylinder contacting portions 206a, 206b formed
towards one end of the print shaft 202. The print cylinder contacting portion
206a
can be in the form of a cylinder of larger diameter than the diameter of the
outer
print shaft 202a. Towards the end of the print shaft which is opposite to the
end
having the print cylinder contacting portion 206a, the outer print shaft 202a
comprises bearing seats 208, 210. The bearing seats 208, 210 house bearings
(not shown) which surround the inner print shaft 202b.
The end of the inner print shaft 202b distal from the print cylinder 200 is
connected to a first servomotor 212. The first servomotor 212 is a linear
servomotor, and in this way it is possible to adjust the longitudinal position
of the
inner print shaft 202b. As shown in Figure 2(b), the other end of the inner
print
shaft 202b is connected to the print cylinder 200. The print cylinder 200 is
sized
so as to be slideable over the surface of the print cylinder contacting
portion
206a. It will be appreciated by the skilled reader that, in this way, the
first
servomotor 212 is able to adjust the longitudinal position of the print
cylinder
200. The longitudinal axis corresponds to the rotational axis of the print
cylinder,
and in practice it is longitudinal. The print cylinder contacting portion 206b
also
contacts part of the print cylinder 200.
The print shaft further comprises a backslash gear 214 which is carried by
a hub 216. The backslash gear 214 is driven by a bull gear (not shown) which
forms part of a conventional decorator apparatus drive mechanism. Cam
followers 218, 220 follow a cam 222. The cam 222 is connected to the hub 216
by a connection member 224. The hub 216 is able to move longitudinally along
the outer print shaft 202a. A key (not shown) underneath the hub 216 permits
this longitudinal movement with respect to the outer print shaft 202a. The cam
CA 02968923 2017-05-25
WO 2016/087876 PCT/GB2015/053725
followers 218, 220 are mounted on a mounting piece 226. The mounting piece
226 is connected to a second servomotor 228. The second servomotor 228 is a
linear servomotor. The second servomotor 228 can be controlled so as to move
the mounting piece 226 which in turn moves the cam followers 218, 220. It will
be appreciated that the effect of this controlled movement is to adjust the
longitudinal position of the hub 216 with respect to the outer print shaft
202a.
This also adjusts the longitudinal position of the backslash gear 214. The
backslash gear 214 carries gear teeth which are inclined at an angle with
respect to the longitudinal axis of the print shaft 202. It will be
appreciated that
longitudinal adjustment of the position of the backslash gear 216 thereby
results
in a rotational adjustment of the print cylinder 200. In this way, the angular
orientation of the print cylinder 200 can be controlled.
Referring back to Figure 1, the camera 22 is positioned to monitor the
blankets 14 after ink has been transferred to them from the inkers 12 but
before
printing onto the cans 18 takes place. The camera is used to detect any
misregistration of one of more of the differently coloured inks which are
applied
to the blankets. Images obtained by the camera 22, or related data, are input
to
a controller device 24. A plurality of cameras may be used instead of a single
camera, and this can enable better 3 dimensional images to be obtained. The
controller device 24 has a graphical interface 24a which in one possible mode
of
operation enables a user to make corrections manually. However, in another
mode of operation the invention provides an automatic correction of any
misregistration of the inks applied by one of more of the inkers 12. The
controller
device 24 utilises a suitable computer program which examines the images
obtained by the camera 22, and recognises any misregistration. The controller
device 24 and its computer program is also adapted to provide suitable control
signals to one or both of the first and the second servomotors of an inker 12
in
order to correct the detected misregistration. For example, if a
misregistration
was detected and it was identified that the cause was that the image applied
to
the blanket by inker 12a was too high, then the longitudinal position of the
print
cylinder used in inker 12a would be lowered in order to correct this
CA 02968923 2017-05-25
WO 2016/087876 PCT/GB2015/053725
11
misregistration. This would be done by controlling the first servomotor
associated with print cylinder of inker 12a so as to retract the inner print
shaft
within the outer print shaft. This has the effect of lowering the print
cylinder.
Another type of misregistration occurs when one of the ink colours is applied
too
far to the left or right of a blanket. In this instance, the controller device
24
identifies which inker 12 is responsible for the misregistration and controls
the
second servomotor associated with this inker device to adjust the position of
the
cam followers with respect to the longitudinal axis of the print shaft. In
this way
the position of the backslash gear is adjusted to so as to move the print
cylinder
clockwise or counter clockwise as required. In this way, the angular
orientation
of the print cylinder is adjusted so as to correct the misregistration. It
will
appreciated that if the controller device detects that a number of inks are
being
applied out of register, then appropriate correction of a plurality of inkers
will
occur. The detection of the misregistrations and the appropriate adjustment of
one or more servomotors to correct the misregistration can be performed in a
number of ways. For example, look up tables or algorithms might be used.
Another alternative is to utilise artificial intelligence.
Although in the arrangement of Figure 1 the camera 22 monitors the
blankets, other variations are possible. For example, the camera may take
images of the cans after printing has taken place. Another possibility is for
the
camera to examine marks on the print plates. In this instance, the print
plates
may each comprise a suitable registration mark such as a dot, line or cross.
The
blankets have corresponding registration features. For example, if a blanket
receives six different colours from six different inkers, and the print plate
of each
inker has a dot as a registration mark, the blankets will have six spaced
apart
dots, one for each colour. Advantageously, the dots may be located in an outer
region of the blanket, for example close to the edge. If there is a
misregistration
in the printing of one of the colours, then this will be visible as a
misregistration
between a registration mark on a print blanket and the corresponding mark
printed b the relevant print plate. This can be readily detected and
appropriate
12
correction may by adjusting the longitudinal position and/or the angular
orientation of the relevant print cylinder.
Figure 3 shows a graphical interface 300 which might be used in conjunction
with the invention. The graphical interface 300 is in the form of a touch
screen. The
touch screen can be used in a manual adjustment mode, where adjustments to the
registration are made by a user. The adjustments made by the user result in
appropriate control of the servomotors of one or more of the inkers.
The correction of misregistration provided by the invention has numerous
advantages. It is possible to quickly correct misregistration without stopping
the
decorator apparatus. Rapid detection of any misregistration reduces spoilage
caused
by misprinting onto cans. If the camera is set up so as to detect
misregistration on the
blankets (or the print cylinders) then it is possible to detect
misregistrations without
any spoilage, because misregistration can be detected without printing on the
cans.
This mode might be employed as part of start up routine, or to make spot
checks on
registration as part of a manual correction mode.
Other forms of servomotor control of the print cylinder can be used. For
example, the actuator system disclosed in US5235911 might be used or adapted
for
use as part of the misregistration correction methodology provided by the
invention.
However, it is believed that the servomotor control system described in
relation to
Figures 1 and 2 provides numerous advantages. It is particularly applicable to
decorators of the Rutherford type, and in fact it can be retrofitted to
existing
Rutherford inkers quite easily. The inner print shaft can be provided by
drilling a
hole through the centre of a standard Rutherford print shaft, and inserting
the inner
print shaft. This servomotor has a low number of wear parts, and it is space
efficient. All of the adjustment components are internal to the inker
cylinder, which
makes maintenance easier. Also, if it is necessary to remove an
CA 2968923 2018-09-14
CA 02968923 2017-05-25
WO 2016/087876 PCT/GB2015/053725
13
inker for maintenance purposes, then it is possible to continue printing onto
cans
using the inkers. Runs can be made either using one colour fewer, or a
substitute inker could be inserted. In this way, maintenance can be performed
without haying to stop operation of the decorator apparatus.
